The invention relates generally to a color electronic reprographic printing system, and more particularly concerns an apparatus for clearing paper jams within the portion of the printing system that transports paper stock from a supply bin to a location point at which an image is transferred to the paper or other copy stock.
The marking engine of an electronic reprographic printing system is frequently an electrophotographic printing machine. In an electrophotographic printing machine, a photoconductive member is charged to a substantially uniform potential to sensitize the surface thereof. The charged portion of the photoconductive member is thereafter selectively exposed. Exposure of the charged photoconductive member dissipates the charge thereon in the irradiated areas. This records an electrostatic latent image on the photoconductive member corresponding to the informational areas contained within the original document being reproduced. After the electrostatic latent image is recorded on the photoconductive member, the latent image on the photoconductive member is developed by bringing toner into contract therewith. The image is subsequently transferred to a copy sheet. The copy sheet is heated to permanently affix the toner image thereto in image configuration.
Multi-color electrophotographic printing is substantially identical to the foregoing process of black and white printing. However, rather than forming a single latent image on the photoconductive surface, successive latent images corresponding to different colors are recorded thereon. Each single color electrostatic latent image is developed with toner of a color complementary thereto. This process is repeated a plurality of cycles for differently colored images and their respective complementarily colored toner. Each single color toner image is transferred to the copy sheet in superimposed registration with the prior toner image. This creates a multi-layered toner image on the copy sheet. Thereafter, the multi-layered toner image is permanently affixed to the copy sheet creating a color copy. The developer material may be a liquid or a powder material.
In the process of black and white printing, the copy sheet is advanced from an input tray to a path internal the electrophotographic printing machine where a toner image is transferred thereto and then to an output catch tray for subsequent removal therefrom by the machine operator. In the process of multi-color printing, the copy sheet moves from an input tray through a recirculating path internal to the printing machine where a plurality of toner images is transferred thereto and then to an output catch tray for subsequent removal. With regard to multi-color printing, a sheet gripper secured to a transport receives the copy sheet and transports it in a recirculating path enabling the plurality of different color images to be transferred thereto. The sheet gripper grips one edge of the copy sheet and moves the sheet in a recirculating path so that accurate multi-pass color registration is achieved. In this way, magenta, cyan, yellow, and black toner images are transferred to the copy sheet in registration with one another.
From time to time, the copy sheet may become jammed at some point along its path inside the machine. In order to enable the user to resolve this problem on his own, reprographic machines are typically designed with portions of the paper path accessible to the user for clearance of the paper jam. In the case of a color reprographic system, a portion of the paper path lies along a generally oval loop, known as a two roll transfer loop, or TRTL, upon which the copy sheet must be recirculated for color copying. In use, the TRTL must be positioned so that it can bring paper very close to an overlying photoconductive surface for image transfer. Copy sheets are routed to the TRTL by a so-called registration module. These portions of the paper path are susceptible to jamming. There is a need to provide for the clearance of the jam in this area of the machine in a manner that is both simple enough for the user to affect and that minimizes the risk of damage to the machine, particularly the sensitive photoconductive surface.